Mailman list import and export
When a user migrates their domain from one hosting company to another, they might quite reasonably want to take their Mailman lists with them. For that matter, if a list owner wants to hand the list off to a different owner, they might reasonably want to move the list to another domain.
The relevant files can be manually provided for the owner by the old hosting company, and manually installed at the new one. But it sure would be nice if for each list on "mail/lists.html", along with "delete" and "change password" and "manage", there was "download..." which took one to page that prompts for to download the list config, the list subscriber db, the list archives (if any), or all of the above; and if there were, as part of the "Create List" form, a way to upload the config files and member db and archives to reconstitute a list from these exports. This pair of features would also have the added benefit of providing the user with a way of backing up their lists, and restoring them from backup, as well as a way to archive and retire old lists that are no longer in use.